A fuel cell system includes a fuel cell which generates electric power by a chemical reaction between hydrogen and oxygen, and a cooling water passage which cools down the fuel cell. In a case where such fuel cell system is left outdoors for a certain period of time or more without operating it, the water in the cooling water passage freezes with decrease in an outside air temperature. As a result, when starting up the fuel cell system next time, it may be impossible to control the temperature of the fuel cell, so that the electric power generation may not be carried out or the efficiency of the electric power generation may deteriorate. Moreover, the fuel cell may be mechanically damaged by the freezing, so that the fuel cell system may not be operated even after unfreezing, or the power generation efficiency may deteriorate. In addition, components, such as a pump, a tank, and a pipe, which cause cooling water to circulate, may be mechanically damaged. As a result, an adequate amount of water may not circulate to cool down the fuel cell, so that the power consumption may increase, the power generation efficiency may deteriorate, or the fuel cell system may not be operated. Further, the water leaking from a damaged portion may cause an electric leakage, and this may cause a risky situation in light of safety.
Known as one example of the fuel cell system which can prevent the freezing is a fuel cell system which includes a temperature sensor which detects an outside temperature and carries out an antifreezing operation when the temperature sensor detects a threshold temperature or lower (see Patent Document 1 for example).
Hereinafter, details of such fuel cell system will be explained. FIG. 5 is a diagram showing a schematic configuration of a conventional fuel cell system described in Patent Document 1.
The fuel cell system described in Patent Document 1 includes: a fuel cell 135; a water supplying line 136 which supplies water to the fuel cell 135; a water processing device 138 which processes city water 137 into pure water; a pressurization pump 139 which feeds the pure water processed in the water processing device 138 to the water supplying line 136; a heater 140 disposed at the water processing device 138; a temperature sensor 141; and a controller 142. The water supplying line 136 includes a water tank 143 and a pressurization pump 144 which supplies water to the fuel cell 135.
When the temperature sensor 141 detects a predetermined temperature or lower, the controller 142 causes the pressurization pump 139 and the pressurization pump 144 to supply the water as antifreezing processing. In addition, the controller 142 turns on a switch of the heater 140 to cause the heater 140 to heat the water processing device 138. With this, even when the outside air temperature is low, it is possible to prevent the freezing of the water supplying line 136 which supplies the water to the fuel cell system, and prevent the damage of the fuel cell system.    Patent Document 1: Japanese Laid-Open Patent Application Publication 2004-207093